Integrated circuit having compensation component

ABSTRACT

An integrated circuit and component is disclosed. In one embodiment, the component is a compensation component, configuring the compensation regions in the drift zone in V-shaped fashion in order to achieve a convergence of the space charge zones from the upper to the lower end of the compensation regions is disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This Utility Patent Application claims priority to German PatentApplication No. DE 10 2006 002 065.0 filed on Jan. 16, 2006, which isincorporated herein by reference.

BACKGROUND

The present invention relates to an integrated circuit having acompensation component with a reduced and adjustable on resistance. Thiscompensation component may be a vertical compensation component oralternatively a lateral compensation component. In one embodiment, thecompensation component is a power field effect transistor.

With respect to compensation components, as is known, there is anextremely extensive prior art concerned with the formation of thecompensation regions. In this respect, as examples and representative offurther documents, reference shall be made in particular to thefollowing:

U.S. Pat. No. 6,630,698 B1 illustrates a field effect transistor inwhich compensation regions in the form of p-conducting pillars have avariable doping, so that the p-conducting pillars have a higher dopingin a region near the source than in a region near the drain. In thiscase, the p-conducting pillars always have the same, constantcross-sectional area.

In U.S. Pat. No. 6,639,272 B2, a likewise variable doping inp-conducting pillars of compensation regions is achieved by means ofdiffering layer thickness of individual epitaxial layers in conjunctionwith the p-conducting pillars having a cross-sectional area that isessentially identical over their length.

Further examples of compensation components comprising compensationregions having a constant cross-sectional area are given by U.S. Pat.Nos. 4,754,310 A1, 5,216,275 A1, 6,621,122 B2 and US 2004/108568 A1.

Furthermore, compensation components using trench technology are knownfor example from U.S. Pat. Nos. 6,512,267 B2, 6,410,958 B1 and 6,433,385B1. In these documents, too, the compensation regions have a largelyconstant cross-sectional area over their length. Only in U.S. Pat. No.6,433,385 B1 mentioned last is a description given of a trenchtransistor having an “extended p-zone” (extended p-conducting zone)which is embedded between oxide-filled trenches and acts as acompensation region, here the trench having a smaller cross-sectionalarea in its lower section than in its upper section, so that thecompensation region has a larger cross-sectional area in deeper regionsof the drift zone than in less deep regions.

U.S. Pat. No. 6,677,643 B2 discloses a compensation component in whichcompensation regions have a larger pitch in proximity to the source thanin proximity to the drain, whereby structures can arise in which acompensation region having a larger cross-sectional area adjoins acompensation region having a smaller cross-sectional area in a verticaldirection between source electrode and drain electrode.

While the conventional compensation components previously mentionedabove all have a vertical structure, U.S. Pat. No. 6,858,884 B2describes a compensation component with a lateral structure, here acompensation region decreasing in terms of its cross-sectional area inthe direction between the source electrode and the drain electrode.However, the compensation region extends directly on the drain side asfar as a highly doped substrate, so that no “pedestal layer” remainsbetween the substrate and the compensation region. This document doesnot discuss any relationships between the form of the compensationregion and the capacitance profile of the compensation component as afunction of the drain-source voltage.

Finally, WO 2005/065385 A2 discloses a compensation component in theform of a field effect transistor in which floating p-conductingcompensation regions lie in the drift zone between source and drain, thediameters of the compensation regions decreasing with increasingdistance from the source electrode. The aim of reducing the diameter isto produce floating p-conducting regions that are intended to achieve anincreased breakdown voltage. Continuous compensation pillars are notprovided in the case of this compensation component.

The numerous documents above are cited by way of example for theextensive prior art with respect to compensation components, to whichattention has already been drawn. It must be emphasized, however, thatin these documents at any rate and also in the other prior artinvestigated, there is no explicit discussion of the relationshipbetween the form of the compensation regions, that is to say thegeometrical shape thereof, and the profile of the capacitance of thecompensation component as a function of the voltage present betweendrain and source, that is to say the output capacitance.

Investigations have now illustrated that especially high-voltage powertransistors embodied as compensation components have the particularproperty that in them the output capacitance is very large given smalldrain-source voltages, but decreases rapidly by several orders ofmagnitude as the drain-source voltage increases, the transition betweenthe range with high output capacitance and the range with no outputcapacitance not in any way being effected in continuous fashion, butrather being effected in stepped fashion.

The above dependence of the output capacitance Coss on the drain-sourcevoltage VDS is qualitatively illustrated schematically in FIG. 1 in alogarithmic representation. The individual steps with which the outputcapacitance of an investigated compensation field effect transistorfalls rapidly as the drain-source voltage VDS increases can clearly bediscerned here.

The physical background for this rapid fall in the output capacitancewill be explained in more detail below. It should be noted here that thefeedback capacitance, that is to say the capacitance between gate anddrain, behaves in similar fashion, and it assumes even smaller valuesthan the output capacitance on account of the drain-source capacitanceadditionally contained in the output capacitance.

FIG. 2 schematically illustrates a p-conducting compensation region 5 inan n-conducting drift zone 2, the pn junction 10 between thecompensation region 5 and the drift zone 2 being in pillar-type form.The source contact lies at the upper edge of FIG. 2, while the draincontact is to be assumed at the lower edge.

If 10 V are present between the drain contact and the source contact inthe switched-on state of the compensation component, then a space chargezone 9 forms which extends all around the pillar-type compensationregion 5 if the interior of the compensation region remains at sourcepotential, but the area surrounding the compensation region 5 in thedrift zone 2 rises slowly up to the drain potential on account of thebulk resistance in the drift zone 2. The space charge zone 9 isparticularly extended at the lower, drain-side end of the compensationregion, so that especially here only a relatively narrowly delimitedregion remains for the current flow in the drift zone 2.

If, then, a plurality of compensation regions lie with theirlongitudinal extent parallel to one another between a source contact anda drain contact and the voltage present between drain and source isincreased continuously, the space charge zones 9 of the parallelcompensation regions will finally converge. At the instant when thespace charge zones 9 converge, the geometry and the effective thicknessof the space charge zone change significantly, which is manifested in astep in the capacitance profile. The steep fall in the outputcapacitance (cf. FIG. 1) and its stepped profile are thereforeultimately caused by the convergence of the space charge zones, in whichcase it should be taken into consideration that the space charge zonesfirst touch one another at the drain-side, lower end of the compensationregions. At this moment when they touch, the entire upper part of thedrift path becomes ineffective for the capacitance, whereby thepronounced steps can be explained.

The steep profile of the output capacitance according to the example ofFIG. 1 results in steep voltage edges, which are highly unfavorable forthe electromagnetic compatibility (EMC behavior) of a circuit that usessuch a compensation component. This holds true in particular for therange of large steps in the profile of the output capacitance.

To summarize, therefore, it can be established that a less steppedprofile of the output capacitance as a function of the drain-sourcevoltage would be highly favorable for the EMC behavior of a compensationcomponent.

For these and other reasons, there is a need for the present invention.

SUMMARY

One embodiment provides an integrated circuit having a compensationcomponent in which the compensation regions in the drift zone areconfigured in V-shaped fashion in order thus to achieve a convergence ofthe space charge zones from the upper to the lower end of thecompensation regions. The stepped capacitance profile is therebysmoothed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the present invention and are incorporated in andconstitute a part of this specification. The drawings illustrate theembodiments of the present invention and together with the descriptionserve to explain the principles of the invention. Other embodiments ofthe present invention and many of the intended advantages of the presentinvention will be readily appreciated as they become better understoodby reference to the following detailed description. The elements of thedrawings are not necessarily to scale relative to each other. Likereference numerals designate corresponding similar parts.

FIG. 1 illustrates the dependence of the output capacitance on thedrain-source voltage in the case of a compensation field effecttransistor.

FIG. 2 illustrates the propagation of the space charge zone around acompensation region with a conventional construction.

FIGS. 3A and 3B illustrate the profile of the pn junction of thecompensation region in the case of the compensation component accordingto the invention (FIG. 3A) and in the case of a conventionalcompensation component (FIG. 3B).

FIGS. 4A and 4B illustrate the propagation of the space charge zone inthe case of a compensation region of the compensation componentaccording to the invention (FIG. 4A) and in the case of a compensationregion of a conventional compensation component (FIG. 4B).

FIG. 5 illustrates, in a comparison, the profile of the outputcapacitance as a function of the drain-source voltage in the case of aconventional compensation component and in the case of a compensationcomponent according to the invention.

FIG. 6 illustrates a sectional illustration through a verticalcompensation component according to the invention.

FIGS. 7A and 7B illustrate a lateral compensation component, FIG. 7Ashowing the latter in perspective, while the construction of thecompensation regions is additionally represented separately in FIG. 7Bfor illustration purposes.

DETAILED DESCRIPTION

In the following Detailed Description, reference is made to theaccompanying drawings, which form a part hereof, and in which is shownby way of illustration specific embodiments in which the invention maybe practiced. In this regard, directional terminology, such as “top,”“bottom,” “front,” “back,” “leading,” “trailing,” etc., is used withreference to the orientation of the Figure(s) being described. Becausecomponents of embodiments of the present invention can be positioned ina number of different orientations, the directional terminology is usedfor purposes of illustration and is in no way limiting. It is to beunderstood that other embodiments may be utilized and structural orlogical changes may be made without departing from the scope of thepresent invention. The following detailed description, therefore, is notto be taken in a limiting sense, and the scope of the present inventionis defined by the appended claims.

One embodiment of the present invention provides an integrated circuithaving a compensation component in which the capacitance profile is assmooth as possible in order thus to obtain a favorable EMC behavior, andwhich is distinguished by a lowest possible on resistance.

In one embodiment, the compensation region or the compensation regionshas or have an ever decreasing cross-sectional area with increasingdistance from the body zone in the direction between the first and thesecond electrode, that is to say in particular in the direction betweensource and drain, so that the compensation region or the compensationregions is or are designed in “V”-shaped fashion. In other words, thecompensation pillars are thus configured in V-shaped fashion.

What is achieved by this configuration of the compensation region or thecompensation regions is that the abovementioned “pinch-off” or “cut-off”in the upper region of the drift path is prevented by the convergingspace charge zones. As a consequence, although the steps in thecapacitance profile (cf. FIG. 1) are still present, they arenevertheless significantly less pronounced, so that the fall in thecapacitance as the drain-source voltage rises is effected more slowlyoverall. This less stepped capacitance profile has a favorable effect onthe EMC behavior of the compensation component.

A further advantage of the V-shaped pillar structure is a reduced onresistance. For the same drain voltage present, the space charge zonepenetrates into the for example n-conducting compensation regionsignificantly less in the case of a component according to the invention(cf. FIG. 4 a) than in the case of a conventional component (cf. FIG. 4b). Since the cross-sectional area of the n-type region has a hugeinfluence on the on resistance, a structure having in that case V-shapedp-conducting pillars has a significantly improved on resistance. If thecompensation component is present in a vertical structure, then it is ofimportance that the compensation region or the compensation regions isor are all configured in contiguous fashion, that is to say has or haveno floating regions. Such floating regions, as can be gathered from WO2005/065385 A2 already mentioned, are therefore not present in the caseof a vertical compensation component according to the invention.

If, by contrast, a compensation component in a lateral structure isinvolved, then it is of importance that a pedestal region of the driftzone additionally remains between the end of the compensation region inthe drift zone and the second zone, that is to say generally the drainzone. In contrast to the lateral semiconductor component disclosed inU.S. Pat. No. 6,858,884 B2, therefore, the compensation region does notreach the drain zone or the highly doped substrate in the case of thelateral compensation component according to the invention.

One embodiment is a field effect transistor. However, the invention isnot intended to be restricted thereto since, in principle, it can alsobe applied to other semiconductor components, such as an IGBT, forexample.

In one embodiment, the drift zone is n-conducting, so that thecompensation regions have p-type conductivity, that is to say are dopedwith boron, for example. In principle, however, opposite conductivityconditions may also be present, so that an n-conducting compensationregion is embedded into a p-conducting drift zone.

In the Figures, the same reference symbols are used in each case formutually corresponding structural parts. FIGS. 1 and 2 have already beenexplained in the introduction.

FIGS. 3A and 3B illustrate the profile of the pn junction 10 between ap-conducting compensation region 5 and an n—conducting drift zone 2 inone embodiment of a compensation component according to the invention(cf. FIG. 3A) and in the case of a conventional compensation component(cf. FIG. 3B), in which case, in order to illustrate the invention, inthe case of the conventional compensation component the compensationpillar, that is to say the compensation region 5, is even somewhatwidened in the direction from source (top) to drain (bottom), while asignificant narrowing of the cross-sectional area of the compensationregion 5 in the direction from source to drain is present in the case ofthe compensation component according to the invention.

FIGS. 4A and 4B illustrate the extent of the space charge zone 9 in theregion of the pn junction 10 between a p-conducting compensation region5 and an n—conducting drift zone 2 in the case of the compensationcomponent according to the invention (cf. FIG. 4A) and in the case of aconventional compensation component (cf. FIG. 4B). In the case of theconventional compensation component (cf. FIG. 4B), the space charge zone9 extends furthest toward the “right” in the lower region of the“pillar”, of the compensation region 5, in this Figure, so that upon the“convergence” of two space charge zones 9 of adjacent compensationregions, a pinch-off of the overlying regions of the drift zone occurs,which in turn causes the stepped and abrupt profile of the outputcapacitance as a function of the drain-source voltage. It can begathered from FIG. 4A that this “pinch-off” does not occur here sincehere the space charge zone 9 does not particularly project in the lowerregion of the “pillar”.

FIG. 5 illustrates the simulated capacitance profiles, the dependence ofthe output capacitance Coss on the drain-source voltage VDS, using asolid line, according to the illustration of FIG. 1, for a conventionalcompensation component (field effect transistor) and using a dash-dottedline for a compensation component according to the invention. In thecase of the compensation component according to the invention, althoughsteps are still present in the capacitance profile, they nonethelessappear in significantly less pronounced fashion. A “smoother” fall inthe output capacitance arises, so that the latter falls more slowly asthe drain-source voltage rises. This can be attributed to the fact that,in the case of the compensation component according to the invention,the individual space charge zones for adjacent “compensation pillars”(cf. FIG. 4A) merge together from top to bottom, so that a pinch-off ofthe overlying drift zone is likewise effected from top to bottom.

In the case of the compensation component according to the invention, onaccount of the extent of the space charge zone explained above, in theswitched-on state, the region remaining for the current flow of theelectrons is preserved such that it has approximately the same widthfrom top to bottom (cf. once again FIG. 4 a).

This means that a significantly increased conductivity and a lower onresistance result for the compensation component according to theinvention in comparison with a conventional compensation componenthaving a customary compensation pillar, so that for example with thegate activated (10 V are present at the gate), the drain currentdepending on the drain voltage is increased by approximately 7.5%. Witha rising drain voltage which increases to 10 V, for example, in the caseof the compensation component according to the invention the draincurrent is in each case increased by approximately 7.5% in comparisonwith the conventional compensation component.

In one embodiment, a vertical compensation component according to theinvention in the form of a field effect transistor having a sourceelectrode S, a drain electrode D and a gate electrode G will beexplained in more detail below with reference to FIG. 6.

An n⁻-conducting drift zone 2 is situated on an n⁺-doped semiconductorsubstrate 1 made of silicon, for example, p-doped body zones 3 beingintroduced into the drift zone. The p-doped body zones 3 contain heavilyn-doped source zones 4 provided with source contacts 6 for the sourceelectrode S. For the rest, an upper main surface 7 of the semiconductorbody is covered by an insulating layer 8 made of silicon dioxide and/orsilicon nitride, on which gate contacts 11 for the gate electrode G arein turn situated.

The lower main surface 12 opposite to the main surface 7 is providedwith a drain contact 13 for the drain electrode D.

P-doped compensation regions 5 are situated in the drift zone 2 in eachcase below the body zones 3 and in a manner adjoining the latter. Inthis embodiment, the compensation regions 5 generally have a V-shapedconfiguration (cf. the dashed lines “V”). They have a cross-sectionalarea which decreases with increasing distance from the main surface 7and decreasing distance to the main surface 12, as can be seen from FIG.6 by virtue of dimensions a and b of the cross-sectional area of thecompensation region 5 (compensation pillar) at the ends of the region 5that are near the source and near the drain, respectively. This“decreasing” of the cross-sectional area is illustrated by thedimensions a and b of the ends of the region 5 that are near the sourceand near the drain, respectively. In this embodiment, the area ratiob²/a² of the cross-sectional area is so small that it is at any ratesmaller than the area ratio which results automatically (also without achange in the implantation openings) on account of the dopantconcentration that is varied in the vertical direction (as proposed,e.g., in U.S. Pat. No. 6,630,698 B1). Values for the area ratio b²/a²are at most 0.95 and in one embodiment 0.5 to 0.8. The compensationregions essentially run parallel to one another.

The compensation regions 5, the body zones 3 and the source zones 4 canbe produced in a customary manner, that is to say for example byindividual epitaxy steps for individual zones 5 ₁, 5 ₂, 5 ₃, 5 ₄, 5 ₅forming a compensation region 5 and by means of implantation and/ordiffusion for the body zone 3 or the source zone 4.

Optionally, an n-conducting pedestal region 14 may additionally bepresent at the lower end of the compensation regions 5 in the drift zone2. If the pedestal region 14 is not present, then the drift zone 2directly adjoins the semiconductor substrate 1. A preferred width forthe pedestal region 14 is at least 2 μm and, for example in the case ofa 600 V component, approximately 10 to 20 μm.

FIGS. 7A and 7B additionally illustrate an exemplary embodiment of thelateral compensation component according to the invention in the form ofa field effect transistor. In this case, FIG. 7A is a perspective view,while FIG. 7B only illustrates the embedding of the compensation regions5 into the drift zone 2 in plan view.

In this embodiment, there are situated on a dielectric substrate 1′ ann⁻-conducting drift zone 2, a p-conducting body zone 3, an n-conductingsource zone 4 embedded into the latter, an n-conducting drain zone 15with an n⁺-conducting contact region 16 for the drain contact 13 of thedrain electrode D, an insulating layer 8 made of silicon dioxide and/orsilicon nitride, a gate layer 11 for the gate electrode G with a gateoxide 17 between the body zone 3 and the gate layer 11, and a sourcecontact 6 for the source electrode S.

According to one embodiment, V-shaped compensation regions 5 areembedded into the drift zone 2, which compensation regions are p-dopedlike the body zone 3, adjoin the latter and run essentially parallel toone another. Situated at the lower end of the compensation regions 5 isan n-doped pedestal region 14, which is at any rate more highly dopedthan the n⁻-doped drift zone 2 and has a somewhat weaker dopingconcentration than the drain zone 15. The width d of the pedestal region14 is once again at least 2 μm and, in the case of a 600 V component,approximately 10 to 20 μm. The pedestal region 14 is present in the caseof the lateral compensation component, whereas it is only optionallyprovided in the case of the vertical compensation component, as wasexplained above.

Silicon is used as semiconductor material for the compensation componentaccording to one embodiment of the invention. However, it is alsopossible to use other semiconductor materials, such as, for example,SiC, etc. Suitable dopants are, as has already been mentioned, boron forthe p-type conductivity and phosphorus or arsenic for the n-typeconductivity. By way of example, aluminum and the like may be used asmaterials for the contact layers.

Although specific embodiments have been illustrated and describedherein, it will be appreciated by those of ordinary skill in the artthat a variety of alternate and/or equivalent implementations may besubstituted for the specific embodiments illustrated and describedwithout departing from the scope of the present invention. Thisapplication is intended to cover any adaptations or variations of thespecific embodiments discussed herein. Therefore, it is intended thatthis invention be limited only by the claims and the equivalentsthereof.

1. A component comprising: a semiconductor body of a first conductivitytype, having a first main surface and a second main surface opposite thefirst main surface; a first electrode arranged on the first mainsurface; a second electrode arranged on the second main surface; asemiconductor substrate of the first conductivity type, thesemiconductor substrate adjoining the second electrode; a pedestalregion of the first conductivity type, the pedestal region adjoining thesemiconductor substrate; a first zone of the first conductivity type,the first zone adjoining the first electrode; a body zone of a secondconductivity type, the body zone adjoining the first electrode; a driftzone of the first conductivity type that lies between the body zone andthe pedestal region, wherein the drift zone is weakly doped relative tothe first zone and the body zone; and at least one compensation regionlocated in the drift zone configured continuously in pillar-type fashionand extends with its longitudinal direction parallel to a connectingdirection between the first and the second electrodes, from the bodyzone to the pedestal region in a manner adjoining the pedestal regionwith the end of the compensation region, wherein the compensation regionhas a tapering cross-sectional area in the direction toward the secondelectrode, wherein the pedestal region is weakly doped relative to thesemiconductor substrate and heavily doped relative to the drift zone;wherein the first conductivity type is an n conductivity type; andwherein the semiconductor substrate, the pedestal region, and the driftzone have a doping sequence: n⁺-doped semiconductor substrate, n-dopedpedestal region, and n⁻-doped drift zone, wherein the n-doped pedestalregion has a weaker doping concentration than the n⁺-doped semiconductorsubstrate, and the n⁻-doped drift zone has a weaker doping concentrationthan the n-doped pedestal region.
 2. The component as claimed in claim1, wherein a thickness of the pedestal region in a direction between thefirst and the second electrodes is at least 2 μM.
 3. The component asclaimed in claim 2, wherein a thickness of the pedestal region is 10 μmto 20 μm.
 4. The component as claimed in claim 1, wherein an area ratiobetween the cross-sectional areas of the compensation region at an endthereof near the second electrode and at an end thereof near the firstelectrode is less than a corresponding area ratio which is establishedin the case of implantation by means of masks with a constant openingand vertically varied doping.
 5. The component as claimed in claim 4,wherein the area ratio between the cross-sectional areas of thecompensation region at an end thereof near the second electrode and atan end thereof near the first electrode is less than 0.95.
 6. Thecomponent as claimed in claim 5, wherein the area ratio between thecross-sectional areas of the compensation region at an end thereof nearthe second electrode and at an end thereof near the first electrode isbetween 0.50 and 0.80.
 7. The component as claimed in claim 1, whereinthe component is a power transistor.
 8. The component as claimed inclaim 1, wherein the compensation region is doped with boron.
 9. Thecomponent as claimed in claim 1, where a plurality of compensationregions runs substantially parallel to one another between the firstelectrode and the second electrode.